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Article

Geochemical and Isotopic Features of Geothermal Fluids Around the Sea of Marmara, NW Turkey

by
Francesco Italiano
1,2,*,
Heiko Woith
3,
Luca Pizzino
4,
Alessandra Sciarra
4 and
Cemil Seyis
5,†
1
OGS, Borgo Grotta Gigante 42/C, 34010 Sgonico, Italy
2
Athanor-Geotech srls, via GregorioVII 396, 00165 Rome, Italy
3
GFZ Helmholtz Centre for Geosciences, 14473 Potsdam, Germany
4
INGV Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma 1, via di Vigna Murata 605, 00143 Rome, Italy
5
TÜBITAK Marmara Research Centre, Earth and Marine Science Institute, 41470 Gebze, Turkey
*
Author to whom correspondence should be addressed.
†
Now at ALSELSAN.
Geosciences 2025, 15(3), 83; https://doi.org/10.3390/geosciences15030083
Submission received: 21 December 2024 / Revised: 27 January 2025 / Accepted: 7 February 2025 / Published: 1 March 2025
(This article belongs to the Section Geochemistry)
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Abstract

:
Investigations carried out on 72 fluid samples from 59 sites spread over the area surrounding the Sea of Marmara show that their geochemical and isotopic features are related to different segment settings of the North Anatolian Fault Zone (NAFZ). We collected fluids from thermal and mineral waters including bubbling and dissolved gases. The outlet temperatures of the collected waters ranged from 14 to 97 °C with no temperature-related geochemical features. The free and dissolved gases are a mixture of shallow and mantle-derived components. The large variety of geochemical features comes from intense gas–water (GWI) and water–rock (WRI) interactions besides other processes occurring at relatively shallow depths. CO2 contents ranging from 0 to 98.1% and helium isotopic ratios from 0.11 to 4.43 Ra indicate contributions, variable from site to site, of mantle-derived volatiles in full agreement with former studies on the NAFZ. We propose that the widespread presence of mantle-derived volatiles cannot be related only to the lithospheric character of the NAFZ branches and magma intrusions have to be considered. Changes in the vertical permeability induced by fault movements and stress accumulation during seismogenesis, however, modify the shallow/deep ratio of the released fluids accordingly, laying the foundations for future monitoring activities.

1. Introduction

It is well known that earthquakes may affect the fluid inventory co- and post-seismically with changes in water level in wells (Wang and Manga, 2010) [1], in temperature (Mogi et al., 1989) [2] and/or chemical composition (Skelton et al., 2014; Woith et al., 2003) [3,4], in the flow rate of gas discharges (Heinicke et al., 2006) [5] and in their chemical and isotopic composition (Hilton, 2007; Mutlu et al., 2012) [6,7].
The geodynamic (geological setting, tectonics, seismicity) context of the area deeply influences the composition and the behavior of the fluids in terms of both chemical and isotopic composition as shallow-originated fluids usually mix with fluids coming from different crustal levels and/or from the upper mantle. Such fluid mixing may change with time due to both seasonal variations and seismogenic processes (stress accumulation, deformation, strain release) [8]. As the fluids have high mobility migrating through fractures and faults and are fast carriers of information on the physico-chemical conditions at depth, they are able to reveal modifications in the equilibrium conditions at depth.
This paper accounts for the gas and water geochemistry including thermal and cold waters as well as free and dissolved gases vented around the Sea of Marmara with the hope that the collected information will be the reference for the future design of continuous monitoring systems. Furthermore, any future changes in the geochemical features of the circulating fluids can be compared with those here presented and discussed. The knowledge of origin, provenance and role of the monitored fluids is necessary for the correct interpretation of any possible recorded temporal change.

2. Seismotectonics of the Marmara Region

The Marmara Sea region constitutes a transition zone between the strike-slip regime of the North Anatolian Fault (NAF) and the extensional regime of the Aegean Sea [9] (Bozkurt, 2001). NAF is a right-lateral strike-slip fault zone separating accreciated material of the Neo-Tethyan ocean (in the western part represented by the Sakarya continent) in the south from older and stiffer basement rocks to the north (Şengör et al., 2005) [10]. While the slip rate along the NAF increases from east to west from 17 to 25 mm/year (Reilinger et al., 2006; Tatar et al., 2012) [11,12], the locking depth decreases from 20 to 17 km (Duman et al., 2016) [13]. West of Bolu (about 31.5° E), the NAF splits into several fault strands separated by pull-apart sub-basins, so that the deformation becomes distributed. Both geological offsets (about 85 km over 5 Ma) as well as present-day motion derived from GPS measurements suggest that 70–90% of the total motion is taken up by the northern strand of the NAF (Armijo et al., 2002; Flerit et al., 2003; Karakaş et al., 2018) [14,15,16]. More than 40 earthquakes with magnitudes above M = 7 occurred in the past 2000 years within the wider Marmara region (Ambraseys and Finkel, 1991; Ambraseys, 2000; Ambraseys and Jackson, 2000; Ambraseys, 2002) [17,18,19,20] (see labelled white stars in Figure 1).
During the past century, a series of strong earthquakes migrated along the NAF from east to west (Stein et al., 1997) [22]. The last events in this series took place in 1999 and ruptured the Izmit and Düzce segments of the NAF with magnitudes of Mw = 7.4 and 7.2, respectively (Barka, 1999; Reilinger et al., 2000; Tibi et al., 2001) [23,24,25]. West of the Sea of Marmara, the last major earthquake occurred in 1912 (Mw = 7.2) along the Ganos fault (Ambraseys and Finkel, 1987) [26]. Thus, the Sea of Marmara constitutes a “seismic gap” (Polonia et al., 2004; Ergintav et al., 2014) [27,28].
Volcanic rocks occur widespread in the southwestern segment on the Biga peninsula. Magmatic activity started in early Miocene with calc-alkaline extrusive as well as intrusive rocks and ended in late Pliocene with alkaline rocks, predominantly basalts (Yilmaz, 1990) [29]. Due to intense seismo-tectonic faulting and tertiary volcanic activity, close to 100 thermal and mineral springs have formed south of the Marmara Sea (Şimşek, 1997) [30]. This is in clear contrast to the area north of the NAF where very few low temperature thermal springs occur. Also, very few earthquakes occurred during the past century and active faults have not been mapped in the oil- and gas-rich (Hoşgörmez and Yalçın, 2005) [31] Thrace basin (Duman et al., 2016) [13]. The lack of deep-reaching fault systems might explain the absence of thermal springs.
An average terrestrial surface heat flow of 60 mW/m2 was determined by Pfister et al. (1998) [32]. High heat flow values (80–110 mW/m2) occur south of the Marmara Sea corresponding to an extensional tectonic regime, whereas normal values (60–72 mW/m2) were found north of the Sea of Marmara. The authors noted that the occurrence of thermal springs does not coincide with heat flow density. Instead, they are controlled by active tectonics with large thermal springs occurring preferentially in trans-tensional regimes. The combination of strike-slip and normal faults seem to promote elevated vertical hydraulic permeability within the crust.
Previous studies on the water and gas geochemistry of mineral and thermal waters as well as their isotopic signatures were carried out for the following areas (the locations are shown in Figure A1, Appendix A): Eskişehir (Yüce et al., 2017) [33], Kuzuluk (Balderer et al., 1991; Greber, 1994) [34,35]; Armutlu (Eisenlohr, 1997) [36]; Oylat (Pasvanoğlu, 2011) [37]; Bursa (Imbach, 1997; Tut Haklidir, 2013) [38,39]; Ekşidere (Yalcin, 1997) [40]; Biga peninsula (Mutlu, 2007; Yalcin, 2007 [41]; Sanliyuksel and Baba, 2011) [40,41,42,43]; Tuzla/Çanakkale (Mützenberg, 1997; Baba et al., 2009) [44,45]. Regional studies on noble gases were provided by Doğan et al., 2009 [46]. Gas emissions located in the deep offshore are CH4-dominated, and were extensively studied during the past 15 years (Geli et al., 2018) [47].

3. Materials and Methods

During two field campaigns in 2013 and 2014 carried out over an area 78,000 km2, a suite of 72 fluid samples including bubbling and free gases as well as cold and thermal waters were collected from 59 sites of natural springs, fountains (türkish: Çeşme) and thermal and cold ponds located around the Sea of Marmara (Figure 2).
In the field, measurements of water temperature, pH, redox potential (Eh) and electrical conductivity (EC) were performed with multi-parameter devices (HACH HQ40D with electrodes). Samples for major cation and anion analyses were filtered using a 0.45 µm nylon filter, and stabilized with ultrapure HNO3. Table 1 lists the full sample suite including coordinates, elevation above the sea level, field data and information on the types of samples. Details on the laboratory techniques and procedures to determine the geochemical features in terms of chemical and isotopic composition of waters and gases (including dissolved and bubbling gas phase) are reported in Appendix B.

4. Results

Data for water composition are listed in Table 2. Table 3 lists the analytical results of the dissolved gases and Table 4 those of the bubbling gases. All data are available in electronic form at the GFZ data archive https://dataservices-cms.gfz-potsdam.de/ (accessed on 1 February 2025) where additional information is provided about the errors of the isotope measurements.

4.1. Water Chemistry

Water samples were collected over a wide range of geo-tectonic, hydrogeological settings and rocks having different origin and mineralogy (sedimentary to volcanic and metamorphic environments). Accordingly, waters display a large variety of physico-chemical features and geochemical compositions as a function of the different processes and mixing (e.g., with seawater) occurring along the hydrological paths, irrespective of their outlet temperature. The outlet temperatures range from 14.1 °C (a Çesme in Yayaköy-Terkirdağ) to 97 °C (a hot spring in Tuzla, Çanakkale). The Çanakkale area hosts the hottest water of the whole Marmara area marked also by the highest values of electrical conductivity (93 mS/cm in Tuzla and 31.5 mS/cm in Kestanbol; Table 1). pH values fall mostly in the range of 6.05–6.96. Extreme values of 9.01 and 3.87 are recorded at an artesian well in Yeniköy (Kocaeli) and in a Çesme at Ekşidere (Balikehir), respectively. The thermal waters with the highest outlet temperature show also the largest content of Na, Ca and Cl. Contrastingly, the lowest Na contents are not related to low-temperature waters. Waters with outlet temperatures in the range of 40–59.7 °C from the areas of Yalova, Bolu, and Eskişehir display Na contents as low as 0.4–0.6 meq/L. The Piper diagram of Figure 3 provides general information on the water types vented around the Marmara Sea. Their spatial distribution of the water chemistry is shown as pie charts in the appendices (Figure A2).
The diagram shows how the thermal and mineral waters collected over the various areas surrounding the Sea of Marmara fall in the different water-type fields although samples collected over the same area (see samples from Bursa) fall in different fields as a consequence of the occurrence of mixing among different water types and WRI (water–rock interaction) processes due to different involved rock types and the extension of the processes.

4.2. Gas Geochemistry

4.2.1. Dissolved Gases

Table 3 lists the analytical results for the dissolved gases showing the presence of variable oxygen amounts and a total amount of gases dissolved in one liter of water which is usually 2–3 orders of magnitude higher than the equilibrium with the atmosphere (Air Saturated Waters, ASW = 16.8 cc/LH2O). Only in a few cases is the total amount of dissolved gases significantly lower than the ASW (e.g., 7.8 cc in a sample from Termal, Yalova or 4.2 cc in samples from the Kocaeli area). The N2/O2 ratio, an indicator for atmospheric contamination, ranges between 2 and 7 (N2/O2 ratio in ASW = 2, Table 3) in the majority of the collected samples, indicating negligible contents of atmospheric components. A few samples from Balikehir, Kocaeli, Çanakkale and Yalova are dominated by N2. The most abundant gaseous component is CO2 with concentrations well above the equilibrium with air-saturated water (ASW; 0.267 mlSTP/LH2O, (Weiss, 1974) [48] ranging from 1 to 2 orders of magnitude above the equilibrium with the atmosphere. Over the area of Bursa (Table 3), we recorded the highest CO2 contents with a pCO2 of 0.88 bar at Çitli, Inegöl (ID = 24, Table 2) and of 0.82 bar at two wells in Kinik, Inegöl and Dümbüldek (ID = 23 and 30, respectively).
CH4 is always present with concentrations ranging from 1.5 × 10−5 mlSTP/LH2O at Tarakli (Sakarya, ID = 49, Table 3) thermal well to 5.49 mlSTP/LH2O at Yayaköy (Tekirdag, ID = 51) mineral spring.
The isotopic composition of the Total Dissolved Carbon (δ13CTDC) ranges between −17.47 ‰ and +2.9 ‰.
The concentrations of light noble gases (He, Ne and Ar) in the dissolved gases vary from 7.6 × 10−5 to 6.3 × 10−3 mlSTP/LH2O, always above the equilibrium with ASW (4.8 × 10−5 mlSTP/LH2O), with an isotopic signature ranging from 0.34 to 4.41 Ra (Ra = 3He/4He atmospheric ratio). The He/Ne ratios are always above 0.267, considered as the reference for an ASW by Holocher et al., 2002 [49].

4.2.2. Bubbling Gases

The bubbling gases are normally not air-contaminated, as shown by the low oxygen contents, except two samples from wells located in Mudurnu and Armutlu (see ID 12 and 56 in Table 4). CO2 is the main gas for most of the collected samples with concentrations above 90 vol.%. Lower CO2 contents (from 23.4 to 76.6 vol.%—see Table 4) are associated with a virtual increase in low-soluble gases (He, N2, CH4). CH4 is present in a wide concentration range: from very low values (e.g., 0.003 vol.% in sample 7 from Çepni, Bolu) to >90 vol.% CH4 from the site Çakırlı (ID = 27, Table 4) at Lake Iznik in the Bursa province. Helium is always enriched by 1 to 3 orders of magnitude with respect to the equilibrium with the atmosphere, both in bubbling and dissolved gases.
The δ13CCO2 values are in the range of −17.23–1.1‰. The He content in the bubbling gases ranges from 1.5 × 10−5 to 5.9 × 10−2 vol.%; the He/Ne ratios vary from 0.31 (the same as atmospheric ratio) to 897 with isotopic helium signatures ranging from 0.18 to 1.60 Ra (uncorrected for atmospheric contamination).

5. Discussion

5.1. Water Geochemistry

Several geochemical “water types” Ca-HCO3, Na-HCO3, Ca-SO4, Na-SO4 and Na (Ca)-Cl (SO4) were identified in the collected samples due to the geologic complexity of the Marmara area. Besides the chemistry, both thermal and mineral waters exhibit a large variability in the physico-chemical parameters (Table 2), driven by the occurrence of different geochemical processes (i.e., water–rock interaction, mixing between aquifers, dissolution of gases of different origins, repeated gas–water interactions, etc.) affecting the final water’s features.
We found Ca-Mg-HCO3 type in cold and warm waters circulating in the Bursa, Bolu and Eskişehir sectors where most of the samples are calcium-dominated. The molar ratios of calcium to magnesium ion concentration as well as calcium vs bicarbonate provide information on the rock type from which a spring is emerging (Figure 4). In waters discharging from carbonate rocks, dolomite dissolution brings the Ca/Mg ratio near unity, whereas a higher ratio (typically in the range of 6–8, White 2010 [50]) is indicative of larger calcite contribution.
Samples from deep wells in Bursa and from Kocaeli have high pH values (>8.0) and very low Ca and Mg contents (Table 1 and Table 2), causing high alkali metal (mainly Na)/alkaline earth metal ratios. The chemical evolution of these waters could derive from a direct ionic exchange with clays: Ca2+ (Mg2+) + Na-X → Ca (Mg)-X2 + Na+ (e.g., Giménez and Morell 1997 [51]).
Cold, warm and thermal Na-HCO3-type waters mainly occur in the Bursa and Sakarya sectors (Figure 5a). Na-HCO3 waters support a combination of WRI (Water–Rock Interaction) and GWI (Gas–Water Interaction) processes due to high CO2 flux and extensive water–rock dissolution, together with ion exchange reactions in deep aquifers at high temperatures. The CO2 can thus be considered as the trigger for the intensified water–rock interactions in a silicate environment and enhance leaching of dissolved ions in the thermal waters (e.g., White, 2005; Navarre-Sitchler and Thyne, 2007 [52,53]).
Na-Cl type waters (Figure 5b) include three thermal waters, one warm sample and four cold waters showing how they circulate both along the Marmara Sea (Istanbul, Tekirdag) and the Aegean Sea (Çanakkale) coastlines as well as in some inner sectors (Lake Iznik, Bursa, Balıkesir, Sakarya). It is generally accepted that Na/Cl > 1 may clearly indicate that the groundwater is far from seawater intrusion as seawater contribution brings a typical Na/Cl ratio around 0.8–0.9. Waters with significantly lower Cl concentrations and Na/Cl >> 1 can be interpreted as Na derived from water–rock interactions, usually released from a silicate weathering reaction of rock-forming minerals (Figure 5b). The molar ratio of Na/Cl for groundwater samples of the study area spans over a small range, from 0.80 to 1.40, very close to the local seawater ratio (0.86).
Thermal waters from Tuzla (Çanakkale) and Kestanbol can be defined as highly saline waters (Stanton et al. 2017 [54]) or classified as a brine (TDS > 35 g/L e.g., Rhoades et al., 1992 [55]). Balderer (1997) [56] and Mützenberg (1997) [44] suggested that the Tuzla brines derived from lateral migration of fossil brines trapped in Miocene sediments. For other Na-Cl-type waters located tens of kilometers away from the closest sea, mixing with deep-seated brines and/or fossil waters must be taken into account to justify their chemical features, as recognized elsewhere in Turkey (e.g., Mutlu & Gulec, 1998) [57].
The Na-SO4 water type is generally associated with metamorphic/volcanic rocks coupled with H2S condensing into the liquid phase as well as from interaction with sulphur/sulphate minerals (e.g., Ellis and Mahon, 1977 [58]). SO4 enrichment (Figure 6) of the hot-water samples from Balıkesir and Çanakkale is not in stoichiometric equilibrium with Ca, suggesting that gypsum/anhydrite cannot be the main source of sulphate in Na-SO4 waters. Na release into solution and calcium and magnesium removal could be the result of a direct ionic exchange with clays, as already inferred from some Na-HCO3 waters.
The acid-sulphate-type water was found just in one sample located in the Balıkesir province called Ekşidere “Gencli Su” (ID = 3). Low temperature and salinity along with the particularly acidic pH (3.87) of this shallow water suggest a probable oxidation of sulphide deposits near the spring. Indeed, sulphides are oxidized when exposed to the environment, due to natural processes or anthropogenic activities, forming sulfuric acid in the presence of humidity (Bigham and Nordstrom, 2000, and references therein) [59]. This process contributes to the acidification of natural waters.

5.2. Stable Isotopes

The measured δ18O–δD values are consistent with a meteoric origin of the groundwater. Figure 7 shows how most of the waters plot between the Global Meteoric Water Line (GMWL, Craig 1961) [60] and the Eastern Mediterranean Meteoric Water Line (EMWL, Gat and Carmi 1970) [61].
The large interval of the measured values, irrespective of outlet temperatures, can be explained considering the size of the studied region and the geographical differences among the sampling sites. A more detailed inspection of the plot of Figure 7 highlights that some mineralized hot, warm and cold waters (TDS in the range 1100–8500 mg/L) show slight to moderate positive shifts in δ18O as in the case of samples 8, 46 and 47.
Their deviation from the MWLs can be attributed to water–rock interaction and/or phase separation processes including exchange between thermal fluids and oxygen-bearing minerals. High-temperature water–rock interaction processes can play an important role in changing not only the chemical (see Section 5.1) but also the isotopic composition of these waters. In particular, the sample from an abandoned well in Kuzuluk (Sakarya, ID = 46) plots off the water lines showing a remarkable δ18O shift (nearly 12‰ V-SMOW), indicating that its isotopic composition is affected by intense evaporation, mixing with evaporated water and/or phase separation; however, an extensive water–rock interaction process cannot be ruled out.

5.3. Gas Composition

The analytical results of the gas phase (Table 3 and Table 4) indicate that the gases released around the Sea of Marmara are dominated either by N2 or CO2. The diagram N2-CO2 of Figure 8 clearly highlights how the bubbling gases are a binary mixture of two end members. The increase in N2 content as CO2 decreases shows that the chemical composition of the bubbling gases is the result of the combination of two effects: mixing between components of different origin and Gas–Water Interactions (GWIs) that lead to CO2 loss due to dissolution and consequent virtual N2 increase. The presence of a third component CH4-dominated is shown in the analytical results (see Table 3 and Table 4). The gas from a Çesme in Çakırlı, located at the northern shore of Lake Iznik (ID = 27 in Figure 8 falling outside the CO2-N2 mixing trend) is mainly composed of methane. See also Figure A3 in the appendices.
The CO2-CH4-N2 triangular diagram of Figure 9 shows how the gases have CO2 contents often above 90 vol.%, with the exception of the N2-dominated gases from Çanakkale and the CH4-dominated gas phase from some sites over the Yalova area. As the atmospheric component for the plotted samples has been removed assuming 0 oxygen content for the deep CO2 and CH4-dominated components, the nitrogen can have either a deep or an atmospheric origin from fluids where oxygen has been removed by bacterial or activity or oxidation processes.

5.4. Helium–Carbon Systematics

As CO2 is the main component in most of the vented fluids, we argue that deep-originated gases feed most of the investigated manifestations. To trace their origin, we take into account that the natural CO2 sources are marked by different δ13C ratios (δ13CMORB = −6.5‰; δ13CLimestones = 0‰, δ13CMarine sediments = −20‰ (Faure, 1986; Javoy et al., 1986; Sano and Marty, 1995) [64,65,66], although mixing of volatiles from different sources and fractionation processes may produce similar δ13C values. The range of measured carbon isotopic compositions for Total Dissolved Inorganic Carbon (TDIC) (−17.47‰ < δ13CTDIC < +3.52‰) and CO2 (−17.23‰ < δ13CCO2 < −1.1‰) allows us to exclude a major role of organic CO2 in the gas mixtures (typically ranging from −70‰ to −25‰; Figure 10). The trend shown in Figure 10a,b suggests that the vented CO2 is not solely controlled by shallow interactions with groundwaters, and that the coexistence of multiple sources has to be considered.
The isotopically heavy carbon δ13CTDIC values (widespread in the Bursa waters and spotty in those circulating in the Çanakkale and BalıkesirBalikesir areas) suggest a contribution from carbonate devolatilization, likely sourced from high-temperature water–rock interactions. Although any high-temperature interaction requires a thermal source (e.g., the mantle and/or magmatic intrusions in the crust (Italiano et al., 2008) [67]), CO2 from those sites (Bursa, Çanakkale and Balıkesir) is isotopically different from those of the Ganos/Tekirdağ area, which are depleted in heavy carbon (δ13C < −17 ‰), probably due to intense GWI.
The measured 3He/4He ratios span from 0.10 to 4.43 R/Rac, indicating a widespread mantle contribution at all sampled sites. Mantle helium does not show any obvious relation to the distribution of volcanic or intrusive igneous rocks (see Figure A4 in the Appendix C.3). It is frequently argued that extensional regimes enhance the helium escape through the crust. If that is true, the southwestern segment of our investigated area would be the most promising—but not confirmed by data. The highest Ra was found at the eastern end of the Ganos fault (ID = 50 in Figure 2). The highest mantle helium contributions (up to 70%, R/Rac 4.3–4.6) were found offshore at a site called “Boris Bubblers”, which is located some kilometers NE of the shoreline where the Ganos fault enters the Sea of Marmara (Burnard et al., 2012) [68]. The authors ruled out present-day magmatic activity and concluded that the release of mantle helium is related to the tectonic setting either coming directly from the mantle via high-permeability faults or else that He stems from cooling magma batches intruded in the shallow crust.
The helium vs. 4He/20Ne isotopic ratios for both dissolved and bubbling gases are shown in Figure 11. Assuming all neon of atmospheric origin, the 4He/20Ne ratio provides an indication of the presence of an atmospheric-derived component in the gas mixture. The plot shows that the dissolved gases (diamonds in the picture) display 4He/20Ne ratios remarkably higher than the ASW although extracted from groundwaters equilibrated with the atmosphere as a consequence of a significant contribution of He-rich gases coming from the CO2-dominated end member.
Helium–carbon relationships in terms of both elemental and isotopic ratios (Figure 12) show the wide range of CO2/3He ratios due to both elemental fractionation (GWI) and mixing between crustal and magmatic sources. Although some of the vented volatiles are highly fractionated, the widespread contribution of a mantle component is evident. The arrows in Figure 12 display the combined effect of regional degassing of magmatic and crustal components (represented by 4He and 3He, respectively) with the GWI inducing CO2 loss for bubbling gases and addition for the ASW-type waters.
Overall, our results indicate that the fluids circulating over the Marmara area are the result of mixing at variable extents of three end members: mantle, crust and atmosphere.

5.5. Fluid Circulation and Fault Activity

While the composition of crustal fluids circulating at relatively shallow depths (namely 3–5 km) is determined by the local geology (for example, the hosting rocks where thermal waters equilibrate or where ground waters interact with gases), the composition of deep fluids is closely influenced by tectonics. Actually, since mantle degassing is not obvious in non-volcanic areas, we argue that if the recorded helium isotopic ratios are higher than the typical crustal values, the release of 3He through lithospheric faults is one of the possibilities. Additionally, as intense mantle degassing along faults cutting 15–25 km of crustal thickness cannot be supported by very low vertical permeability (Italiano et al., 2000) [69], mantle-derived volatiles may be related to melts intruded in crustal levels as already observed in Southern Apennines by Italiano et al., 2000 [69]. Alternatively, the ductile to fragile transition layers for the various NAFZ segments occur at shallower levels than 15–25 km.
Evidence that fluids with a variable—although sometimes significant—mantle component are vented over the whole Marmara region implies a widespread lithospheric character of the various NAFZ branches, highlighting the possibility of detecting variations in the fault behavior from temporal and spatial changes in the mixing proportion of the deep and shallow fluid components. Unfortunately, repeated measurements of helium isotopes are rare as the compilation of published data shows (see Appendix C).
In the past, the most significant decrease in the mantle helium contribution was observed at Mudurnu and Efteni (ID = 11 and 9), both located in the easternmost segment in the province of Bolu. In 1995, i.e., before the Izmit and Düzce earthquakes of 1999, Ra values of 4.65 and 1.83 were observed at Mudurnu and Efteni, respectively. In 2000 and the following years, the Ra values decreased to 2.19 and 0.81, respectively (see Table A1 in the appendices). Dogan et al. (2009) [46] assumed that the decrease in mantle helium at Mudurnu might be related to a large post-seismic increase in water level. Mudurnu is a free-flowing artesian well and we can confirm from our own observations that the water flow almost doubled after the 1999 earthquakes. Interestingly, the physico-chemical parameters were not affected by the earthquakes (Woith et al., 2000) [70]. For Efteni, the authors state that the reduced mantle helium was probably caused by a decreased permeability of the faults. Again, we confirm from our own observations that the water stopped flowing immediately after the Düzce earthquake of 13 November 1999. Two weeks after the event, the flow rate recovered to pre-event levels and we could take a water sample. The chemical composition did not change, but we measured a 4-fold increase in dissolved CO2 (Woith et al., 2000) [70].

6. Conclusions

The MARsite project enabled us to collect enough data (59 sites) for the evaluation of the background geochemical features of fluids venting over the study area. All the collected information indicates that the fluids circulating over the Marmara Sea area are the result of mixing of three gaseous end members (mantle, crust and atmosphere) at variable extents. Thermal and mineral waters equilibrated at various depths in a wide range of hosting rocks.
  • Water geochemistry: Water temperatures range from 14 °C to 97 °C, and electrical conductivity from 198 µS/cm to 93 mS/cm. Geochemical “water types” Ca-HCO3, Na-HCO3, Ca-SO4, Na-SO4 and Na (Ca)-Cl (SO4) indicate the geologic complexity of the Marmara area driven by the occurrence of different geochemical processes (i.e., water–rock interaction, mixing between aquifers, dissolution of gases of different origins, repeated gas–water interactions, etc.) affecting the final water’s features.
  • Stable isotopes: The measured δ18O–δD values are consistent with a meteoric origin of the groundwater and denote the occurrence, sometimes significant, of evaporation effects.
  • Gas composition: Bubbling gases are a binary mixture of two end members, namely CO2 and N2. Only a few samples contain CH4 in significant amounts. The increase in N2 and CO2 decreases shows that the chemical composition of the bubbling gases is the result of the combination of two effects: mixing between components of different origin and Gas–Water Interactions (GWIs) that lead to CO2 loss due to dissolution and consequent virtual N2 increase.
  • Helium–carbon systematics: The measured 3He/4He ratios span from 0.11 to 4.43 R/Ra, indicating a widespread mantle contribution at all sampled sites. Mantle helium does not show any obvious relation to the distribution of volcanic rocks. Spatial variations of the 3He/4He isotopic ratios are possibly related to fault segments with different rock permeability. High isotopic ratios do not exclude the presence of magmatic intrusions in the shallow crustal levels.
The geochemical features of the fluids, including cold and hot waters and the dissolved and bubbling gases vented along the NAF segments around the Sea of Marmara, are the consequence of interactions between a deep (mantle-derived) component that mixes at variable extents with groundwater circulating at variable levels in the shallow crust. Changes in geochemical parameters have been reported in coincidence with seismic events and we argue that they should be expected during the entire seismogenic cycle, even in the absence of seismic energy release (e.g., Italiano et al., 2009 [71], Wang and Manga, M., 2015 [72], Sato et al. 2020 [73] and references therein).
Since changes in vertical permeability and microfracturing induced by stress accumulation and crustal deformation play a significant role in the fluid circulation, they are responsible for temporal changes observable in the fluids’ geochemistry. This close relationship between fluid geochemistry, stress accumulation and fault behavior represents the scientific reference for the development of a multidisciplinary monitoring activity over the Marmara region, where fault failures are expected. Our results can be the reference for future periodical geochemical surveys and for the selection of the most suitable sites to set up automatic stations for continuous monitoring activity.

Author Contributions

F.I. and H.W. developed the conception and design of the study. F.I., H.W. and C.S. collected fluid samples during 2014. Analytical job carried out at INGV where L.P. and A.S. worked on the water analyses. F.I. wrote the first draft of the manuscript. C.S. drafted the original version of the database and worked on data validation. F.I. and H.W. took care of funding acquisition and project administration. All authors have read and agreed to the published version of the manuscript.

Funding

This research has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement N° [308417] (MARsite project) co-funded by the European Commission THEME [ENV.2012.6.4-2].

Data Availability Statement

Data are available at http://dataservices.gfz-potsdam.de/portal/ (accessed on 1 February 2025).

Acknowledgments

The paper is a scientific contribution to the MARsite project. Field work and fluid monitoring were supported by TÜBITAK Marmara Research Centre, Earth and Marine Science Institute (Gebze, Turkey), Department of Geophysics, Kocaeli University (Kocaeli, Turkey), and GFZ German Research Centre for Geosciences (Potsdam, Germany). Comments and suggestions from two anonymous reviewers improved the earlier version of the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Appendix A

Locations

Location names are shown in Figure A1. Note that there are two sites called “Tuzla” in the investigation area (site ID = 34 south of Çanakkale and 43 east of Istanbul). Throughout the text “Tuzla” refers to site ID = 34.
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Figure A1. Map showing locations mentioned in the text. Numbers refer to sampling sites of this study (see Table 1).
Figure A1. Map showing locations mentioned in the text. Numbers refer to sampling sites of this study (see Table 1).
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Appendix B

Appendix B.1. Water Analyses

The concentration of the major ions was determined by liquid chromatography (Dionex 2001) using a Dionex CS-12 and a Dionex AS4A-SC column for cation and anion determinations, respectively. Water isotopic composition in terms of δ18O and δD was determined by mass spectrometry by equilibration technique (Epstein and Mayeda, 1953 [74] for oxygen) and water reduction (hydrogen production by using granular Zn, Kendall and Coplen, 1985) [75], respectively, according to the procedure described in Yuce et al. (2014) [76] on unfiltered samples.
Measurements were carried out using a Finnigan Delta Plus mass spectrometer (Hydrogen) and an automatic preparation system coupled with an AP 2003 IRMS (Oxygen). The O and H isotopic data are expressed as per mil deviation from the V-SMOW standard (Vienna Standard Mean Oceanic Water) using the conventional δ18O and δD notation (δ = [(Rsample/Rstandard) − 1] × 1000 (‰) where R represents the 18O/16O or 2H/1H isotopic ratio). Analytical precision for each measurement is better than 0.2‰ for δ18O and 1‰ for δD.
The partial pressure pCO2 was computed by using the PHREEQC code v. 2.12 (Parkhurst and Appelo, 1999) [77], operating with the Lawrence Livermore National Laboratory (LLNL) database, having as input temperature, pH, Eh, alkalinity and major elements.

Appendix B.2. Gas Analyses

The chemical composition and the isotopic ratios of He and C of the bubbling and dissolved gases were determined using the same analytical equipment. The dissolved gases were extracted after equilibrium was reached at constant temperature with a host gas (high-purity argon) injected in the sample bottle through the rubber septum (details in Italiano et al., 2009, 2014 [78,79]). Chemical analyses were carried out by gas chromatography (Perkin Elmer Clarus500 equipped with a double TCD-FID detector) using argon as the carrier gas. Typical uncertainties are within ± 5%. The composition of the dissolved gas phase was calculated from the gas chromatographic analyses by combining the solubility coefficients (Bunsen coefficient in mlgas/LH2O) of each gas species at the equilibration temperature of the thermostatic bath, the extracted gas (ml) and the water sample volumes (carefully measured at the equilibration temperature) as in equation (A1):
GC = ([Ggc] × * Vγe + ([Ggc] × ßG × VW))/VW × Vγe/Vγi/100
where GC is the concentration of the selected gas, Ggc is its concentration measured by gas chromatography (vol%), Vγe and Vγi represent the extracted and the introduced gas volumes, respectively, ßG is the Bunsen coefficient of the selected gas species and VW is the volume of the collected water sample.
Helium isotope analyses were performed on gas fractions extracted following the same procedure as for the gas chromatography, and purified following methods described in the literature (Sano and Wakita, 1988; Hilton, 1996; Italiano et al., 2001) [80,81,82]. After cryogenic separation of He from Ne, the purified helium fraction (either of dissolved or bubbling gases) was analyzed with a static vacuum mass spectrometer (GVI5400TFT) that allows the simultaneous detection of 3He and 4He ion beams, thereby keeping the 3He/4He error of measurement to very low values. Typical uncertainties in the range of low 3He samples are within ±1%. During the same analytical procedure the 4He/20Ne ratio was measured by peak intensities on the mass spectrometer.
The carbon isotopic composition of CO2 and CH4 in bubbling gases was determined by a continuous flow mass spectrometer (Finnigan MATDeltaS). The sealed water samples were used for the carbon isotopic composition of total dissolved carbon (δ13CTDC). It was measured in a 2 ml water sample introduced into containers injected with high purity helium to remove atmospheric CO2. The water samples were acidified with phosphorus pentoxide in an auto-sampler to ensure complete release of CO2 from acidified waters. CO2 was then directly admitted to a continuous flow mass spectrometer (AP2003). All the results are reported in δ‰ units relative to the V-PDB (Vienna-Pee Dee Belemnite) standard; the standard deviation of the 13C/12C ratio was ± 0.2 ‰.
Argon isotopes were measured only in bubbling gases with a multi-collector noble gas mass spectrometer (ARGUS, GVI) specifically designed for simultaneous collection of 40Ar, 38Ar and 36Ar isotopes on five Faraday collectors. 40Ar is detected on a collector with a 1011 ohm resistor and the remaining isotopes are collected and measured on four detectors fitted with 1012 ohm resistors (for 36Ar to 39Ar). The equipment is connected to a stain-less steel purification line where 0.1 mL of gas are introduced and purified by cold and hot getter pumps (reactive gas removal). Measuring errors are estimated to be better than ±1%.

Appendix C

Appendix C.1. Water Chemistry

Figure A2 shows the chemical composition of the thermal and mineral waters around the Sea of Marmara.
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Figure A2. Chemical composition of thermal and mineral waters around the Sea of Marmara. The diameter of the pies scales with the specific electrical conductivity of the waters. Small circles in the centre of the pies indicate the water temperature: blue—cold (<20 °C); orange—hot (>40 °C).
Figure A2. Chemical composition of thermal and mineral waters around the Sea of Marmara. The diameter of the pies scales with the specific electrical conductivity of the waters. Small circles in the centre of the pies indicate the water temperature: blue—cold (<20 °C); orange—hot (>40 °C).
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Appendix C.2. Gas Composition

Figure A3 shows the gas composition in the investigation area.
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Figure A3. Gas composition of thermal and mineral waters around the Sea of Marmara. Small white circles in the centre of the pies indicate bubbling gases.
Figure A3. Gas composition of thermal and mineral waters around the Sea of Marmara. Small white circles in the centre of the pies indicate bubbling gases.
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Appendix C.3. Helium Isotopes

The spatial helium R/Ra distribution is shown in Figure A4.
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Figure A4. Helium isotope ratios given in R/Ra at mineral and thermal waters around the Sea of Marmara. Light purple areas depict Tertiary volcanic rocks, hatched areas mark intrusive igneous rocks of Paleozoic to Cenozoic age. Light and dark gray areas indicate Mesozoic and Paleozoic rocks, respectively. White areas are Paleogene to Quaternary sediments. Simplified geology modified from Pawlewicz et al. (1997) [83].
Figure A4. Helium isotope ratios given in R/Ra at mineral and thermal waters around the Sea of Marmara. Light purple areas depict Tertiary volcanic rocks, hatched areas mark intrusive igneous rocks of Paleozoic to Cenozoic age. Light and dark gray areas indicate Mesozoic and Paleozoic rocks, respectively. White areas are Paleogene to Quaternary sediments. Simplified geology modified from Pawlewicz et al. (1997) [83].
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Table A1 lists a compilation of helium isotope values for the wider Marmara Sea area.
Table A1. Temporal evolution of helium R/Ra values between 1984 and 2014 compiled from various sources [44,46,84,85,86,87,88,89,90,91,92]. Data for 2013 and 2014 are from this study.
Table A1. Temporal evolution of helium R/Ra values between 1984 and 2014 compiled from various sources [44,46,84,85,86,87,88,89,90,91,92]. Data for 2013 and 2014 are from this study.
SiteID1984198519891990199219931995 g20002001 i2002 i2003 i2004 i2005 j20132014
Manyas Kizik6 0.41 k0.49
Derdin80.75 a 0.75 0.610.59
Efteni91.93 a 1.830.71 h 0.81 i0.760.760.880.830.66
Mudurnu114.78 a 4.652.19 h,i 2.302.222.182.812.09
Bursa Çekirge140.52 b0.60 b 0.48 d 0.48 0.46
Bursa Kükürt15 0.44 c0.45 d 0.540.46
Oylat20 0.660.67
Keramet260.26 a 0.29 0.340.29
Gemlik290.05 b 0.15 f 0.13
Kestanbol33 0.80 k 0.87
Tuzla340.42 a 1.47 e 1.44 k 1.55
Tuzla Büyüyk Iç.43 0.42 0.52 0.58
Kuzuluk47 0.63 d 0.63 0.63
Sarköy50 4.85 4.80
Armutlu530.22 a 0.24 f 0.41 0.250.22
Yalova Termal59 0.27 f 0.29 h,i 0.290.280.320.280.29
a—Stone (1986); b—Gülec (1988); c—Imbach (1992); d—Greber (1992); e—Mützenberg (1997); f—Eisenlohr (1995); g—Ercan (1995); h—Gülec (2002); i—deLeeuw (2010); j—Dogan (2009); k—Mutlu (2008).

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Figure 1. Map of historic earthquakes in the wider Marmara region compiled from various sources [17,18,19,20]. Labels indicate the year of the event for magnitudes M ≥ 7. White lines depict active faults according to the General Directorate of Mineral Research and Exploration (MTA) [21]; off-shore faults are taken from Armijo et al. (2002) [14]. Orange and red lines indicate the ruptures related to the Ganos earthquake of 1912 and the Izmit/Düzce events of 1999, respectively.
Figure 1. Map of historic earthquakes in the wider Marmara region compiled from various sources [17,18,19,20]. Labels indicate the year of the event for magnitudes M ≥ 7. White lines depict active faults according to the General Directorate of Mineral Research and Exploration (MTA) [21]; off-shore faults are taken from Armijo et al. (2002) [14]. Orange and red lines indicate the ruptures related to the Ganos earthquake of 1912 and the Izmit/Düzce events of 1999, respectively.
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Figure 2. Map of fluid sampling sites around the Sea of Marmara. Symbols indicate color-coded water temperatures. Small white circles depict sites with bubbling gases. Values are sample numbers used in this study (see Table 1). Names of geographic areas investigated are given.
Figure 2. Map of fluid sampling sites around the Sea of Marmara. Symbols indicate color-coded water temperatures. Small white circles depict sites with bubbling gases. Values are sample numbers used in this study (see Table 1). Names of geographic areas investigated are given.
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Figure 3. Piper diagram of the water samples as a function of the geographical areas. Sample labels as the ID numbers in Table 2.
Figure 3. Piper diagram of the water samples as a function of the geographical areas. Sample labels as the ID numbers in Table 2.
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Figure 4. Ca vs Mg (a) and HCO3 (b). The occurrence of GWI processes allows CO2 dissolution that is responsible for the observed geochemical features related to WRI resulting in dolomite and calcite dissolution to various extents. Sample labels are the same as the ID numbers in Table 2.
Figure 4. Ca vs Mg (a) and HCO3 (b). The occurrence of GWI processes allows CO2 dissolution that is responsible for the observed geochemical features related to WRI resulting in dolomite and calcite dissolution to various extents. Sample labels are the same as the ID numbers in Table 2.
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Figure 5. Na vs HCO3 (a) and Na vs. Cl (b). The occurrence of WRI and GWI processes is responsible for the observed geochemical features. Blue star symbol = sea water. Sample labels are the same as the ID numbers in Table 2. Symbol colors are as shown in Figure 3.
Figure 5. Na vs HCO3 (a) and Na vs. Cl (b). The occurrence of WRI and GWI processes is responsible for the observed geochemical features. Blue star symbol = sea water. Sample labels are the same as the ID numbers in Table 2. Symbol colors are as shown in Figure 3.
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Figure 6. Ca-SO4 plot showing that gypsum dissolution is not the main process responsible for the SO4 ions, with the water chemistry being a consequence of WRI and GWI processes. Sample labels are the same as the ID numbers in Table 2. SW = sea water.
Figure 6. Ca-SO4 plot showing that gypsum dissolution is not the main process responsible for the SO4 ions, with the water chemistry being a consequence of WRI and GWI processes. Sample labels are the same as the ID numbers in Table 2. SW = sea water.
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Figure 7. δ18O–δD plot for the collected waters. Samples fall between the two reference lines representing the EMMWL (Eastern Mediterranean Meteoric Water Line; Hatvani et al., 2023 [62]) and the GMWL (Global Meteoric Water Line; Rozanski et al., 1993 [63]). BMWL refers to the Bursa local meteoric water line proposed by Imbach et al. (1997) [38]. Sample labels are the same as the ID numbers in Table 2.
Figure 7. δ18O–δD plot for the collected waters. Samples fall between the two reference lines representing the EMMWL (Eastern Mediterranean Meteoric Water Line; Hatvani et al., 2023 [62]) and the GMWL (Global Meteoric Water Line; Rozanski et al., 1993 [63]). BMWL refers to the Bursa local meteoric water line proposed by Imbach et al. (1997) [38]. Sample labels are the same as the ID numbers in Table 2.
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Figure 8. CO2-N2 relationships for bubbling (filled circles) and dissolved (diamond) gases indicating the presence of two end members in the gas phase, namely the shallow atmospheric-derived N2 component and the deep-originated CO2, vented over the Marmara area that mix at variable extents. Numbers indicate the sample IDs as in Table 1.
Figure 8. CO2-N2 relationships for bubbling (filled circles) and dissolved (diamond) gases indicating the presence of two end members in the gas phase, namely the shallow atmospheric-derived N2 component and the deep-originated CO2, vented over the Marmara area that mix at variable extents. Numbers indicate the sample IDs as in Table 1.
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Figure 9. CO2-CH4-N2 triangular diagram of the bubbling (filled circles) and dissolved (diamonds) gases showing the relative contents of the three end members N2, CO2 and CH4. We plotted the N2 excess with respect to the atmospheric nitrogen. The arrows highlight the GWI processes (CO2 loss and increased N2 and CH4 contents) as well as mixings due to CO2 addition from various sources that significantly changed the composition of the pristine gas phase. The numbers beside the symbols indicate the site as listed in Table 1.
Figure 9. CO2-CH4-N2 triangular diagram of the bubbling (filled circles) and dissolved (diamonds) gases showing the relative contents of the three end members N2, CO2 and CH4. We plotted the N2 excess with respect to the atmospheric nitrogen. The arrows highlight the GWI processes (CO2 loss and increased N2 and CH4 contents) as well as mixings due to CO2 addition from various sources that significantly changed the composition of the pristine gas phase. The numbers beside the symbols indicate the site as listed in Table 1.
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Figure 10. CO2 content vs δ13CCO2 for the bubbling gases (a) and for δ13CTDIC of the dissolved gases (b). The plots depict a clear direct correlation between isotopic ratios and CO2 and HCO3 contents. The contemporary trends denote the fractionation with quantitative loss of gaseous CO2 and its heavy isotope as well as the occurrence of further fractionation processes. The occurrence of similar trends followed by samples from different sites around the Marmara area suggests that the vented CO2 is not solely controlled by shallow interactions with groundwaters, and that the coexistence of multiple sources has to be considered.
Figure 10. CO2 content vs δ13CCO2 for the bubbling gases (a) and for δ13CTDIC of the dissolved gases (b). The plots depict a clear direct correlation between isotopic ratios and CO2 and HCO3 contents. The contemporary trends denote the fractionation with quantitative loss of gaseous CO2 and its heavy isotope as well as the occurrence of further fractionation processes. The occurrence of similar trends followed by samples from different sites around the Marmara area suggests that the vented CO2 is not solely controlled by shallow interactions with groundwaters, and that the coexistence of multiple sources has to be considered.
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Figure 11. Helium isotopic ratios (uncorrected R/Ra values) and 4He/20Ne relationships for both dissolved and bubbling gases. The theoretical lines represent binary mixing trends of atmospheric helium with mantle-originated and crustal helium. The assumed end members for He-isotopic ratios and 4He/20Ne ratios are ASW (1 Ra, He/Ne = 0.267: Holocer et al., 2002) [49]; 8Ra for a MORB-type mantle; and 3.5 Ra for contaminated mantle; crust 0.05Ra and 4He/20Ne ratio = 10,000. Filled circles = bubbling gases; filled diamonds = dissolved gases. Sample IDs are as reported in Table 3. All error bars are within the symbol size.
Figure 11. Helium isotopic ratios (uncorrected R/Ra values) and 4He/20Ne relationships for both dissolved and bubbling gases. The theoretical lines represent binary mixing trends of atmospheric helium with mantle-originated and crustal helium. The assumed end members for He-isotopic ratios and 4He/20Ne ratios are ASW (1 Ra, He/Ne = 0.267: Holocer et al., 2002) [49]; 8Ra for a MORB-type mantle; and 3.5 Ra for contaminated mantle; crust 0.05Ra and 4He/20Ne ratio = 10,000. Filled circles = bubbling gases; filled diamonds = dissolved gases. Sample IDs are as reported in Table 3. All error bars are within the symbol size.
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Figure 12. CO2/3He–4He. The plot shows how the vented gases are a mixture of two main components: magmatic-type and crustal-originated. Circles = bubbling gases; diamonds = dissolved gases. The arrows display the main trends affecting the composition of the gas phase.
Figure 12. CO2/3He–4He. The plot shows how the vented gases are a mixture of two main components: magmatic-type and crustal-originated. Circles = bubbling gases; diamonds = dissolved gases. The arrows display the main trends affecting the composition of the gas phase.
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Table 1. Sampling sites (listed in alphabetical order of investigated areas shown in Figure 2) around the Sea of Marmara. Geographic coordinates in decimal degrees, altitude above sea level (mNN) and indications on the location types (Çesme—fountain) are reported besides the field data of water temperature (wT in °C), electrical conductivity (EC in µS/cm at 25 °C), pH, EhSHE (mV), and dissolved oxygen (mg/L). The presence of bubbling gases is also reported (gas). Kapl.—Kaplıcası (bath); MS—Maden Suyu (mineral water). For sample locations see Figure 2.
Table 1. Sampling sites (listed in alphabetical order of investigated areas shown in Figure 2) around the Sea of Marmara. Geographic coordinates in decimal degrees, altitude above sea level (mNN) and indications on the location types (Çesme—fountain) are reported besides the field data of water temperature (wT in °C), electrical conductivity (EC in µS/cm at 25 °C), pH, EhSHE (mV), and dissolved oxygen (mg/L). The presence of bubbling gases is also reported (gas). Kapl.—Kaplıcası (bath); MS—Maden Suyu (mineral water). For sample locations see Figure 2.
IDLonLatmNNAreaSiteTypeDatewTECpHEhSHEOxyGas
126.885739.589411BalıkesirEdremit Güre IGJ-1well 167 m03.09.201450.711148.59281.2
227.561440.0295250BalıkesirEkşiderespring03.09.201437.93737.391622.1
327.579040.0050225BalıkesirEkşidere “Gencli Su”Çesme03.09.201419.31983.874612.5
427.771939.8761130BalıkesirIlica (Balya)spring29.05.201355.411938.12189 x
528.133040.093920BalıkesirIlicaboğazi Susurlukspring30.05.201358.631706.70
04.09.201453.033406.73 1.7
627.910640.065434BalıkesirKızık (Manyas)well 30 m30.05.201351.118076.64241
731.518940.6746821BoluÇepni Aci Suspring04.06.201321.519576.164290.3x
831.241440.7212423BoluDerdinspring04.06.201330.581806.671181.1x
931.027940.7607136BoluEfteni Kapl.spring04.06.201342.531306.40590.1x
1031.007440.5987572BoluIlica (Taşkesti)well05.06.201359.814108.7044
1131.240140.45911044BoluMudurnu Babaswell 125 m, artes.05.06.201338.111866.432140.7
1231.239840.45951055BoluMudurnu Babas NWwell 250 m, artes.05.06.201339.411786.521391.9x
1331.241440.46041063BoluMudurnu Babas NEwell 400 m, artes.05.06.201340.211746.371840.1
1429.018340.2001224BursaÇekirge Vakifbahcespring30.05.201346.15676.96241
04.09.201446.56017.043421.2
1529.036840.1989143BursaKükürtlü Uni Hospitalspring03.06.201364.314076.65224
08.09.201462.914306.84−213.9
1629.040440.1985127BursaKükürtlü BK2well 400 m, artes.03.06.201318.513057.65−260.1x
08.09.201425.711418.24−2860.3x
1729.046640.1973135BursaKükürtlü BJ-3well 750 m, artes.03.06.201316.56678.29−561.9
1829.079540.0403566BursaÇaybaşi Uludağ MSwell 32 m05.09.201422.221796.371523.9
1929.088440.0372590BursaÇaybaşi Özkaynak MSspring08.09.201420.113076.082133.3
2029.586339.9274711BursaOylat Eski Hamamspring10.06.201340.77357.383944.2
2129.671540.0128465BursaÖzlüce “Suyu Çesme”Çesme10.06.201315.825106.222541.5
2229.651040.0100358BursaKınık Maden Suyuwell10.06.201314.523006.462943.6
2329.648940.0151353BursaKınık Maden Suyu Nwell, artesian10.06.201317.265106.581790.2x
2429.636240.0181370BursaÇitli (Inegöl)Çesme10.06.201319.779806.701340.1x
2529.590040.3708298BursaYk. Gölüce “Tuzlu Su”Çesme02.06.201316.835807.47−565.7
2629.476640.4980109BursaKeramet Ilicaspring in lake02.06.201331.99026.754441.0x
2729.445240.497786BursaÇakırlı CH4-Çesmewell 86 m02.06.201318.35807.78 0.0x
2829.308940.4679102BursaOrhangazi Ilıpinarspring in lake02.06.201317.06667.013646.7
2929.160440.42345BursaGemlik Merkez Kapl.well, artesian03.06.201336.24257.422325.3
3028.431539.948775BursaDümbüldekwell, artesian30.05.201350.625206.38165
3128.429539.952667BursaDümbüldek springspring30.05.201316.329306.05204 x
04.09.201419.430506.291312.4x
3228.389439.996459BursaYalıntaş Aci SuÇesme04.09.201419.521336.144110.3
3326.191639.744933ÇanakkaleKestanbolwell02.09.201475.7315806.28992.8
3426.178839.567739ÇanakkaleTuzlaspring02.09.201497.0930006.741093.9x
3527.241340.0923195ÇanakkaleKirkgecit Kapl.spring29.05.201352.16629.0324 x
3626.974539.9169181ÇanakkaleBardakçılar Dağ Kapl.spring29.05.201350.716088.18264 x
3727.155739.8442296ÇanakkaleYenice Hıdırlar Kapl.spring29.05.201382.79557.50131 x
03.09.201483.210738.08−184.1x
3830.168039.8143859EskişehirInönü Ilicaspring09.06.201327.44317.513845.8
3930.519839.7738790EskişehirEskişehir Hamamyoluwell09.06.201345.74987.403193.3
4031.037639.6878817EskişehirUyushamam E-8well 45 m08.06.201315.618145.993891.0x
4131.060039.6794800EskişehirUyushamamspring08.06.201328.312756.442090.5x
4231.722339.4423921EskişehirHamamkarahisar Çardakspring08.06.201335.07687.132243.6
4329.294840.84493IstanbulTuzla “Büyük Içmeler”well 158 m, artes.31.08.201420.4147406.86359
4429.877340.697528KocaeliYeniköywell, artesian04.06.201331.53819.10−361.1
4529.877240.696737KocaeliYeniköy Jazlik Ilicaspring04.06.201329.7372.48.9889
4630.647740.6210111SakaryaKuzuluk Wwell31.08.201419.680206.541343.3x
4730.657040.6257127SakaryaKuzuluk K-3well 160 m31.08.201472.037506.89−111.8x
4830.363240.4715412SakaryaAhibaba Ilık Suspring05.06.201324.922106.292390.8x
4930.428240.3989415SakaryaTaraklıwell, artesian05.06.201342.59486.621041.6
5027.259640.7355221TekirdağHoşköy Özkaynak MSspring01.09.201418.238106.80491.4
5127.212540.7128242TekirdağYayaköy (Şarköy)Çesme28.05.201314.1148006.95−164
5227.106440.6847158TekirdağGölcükÇesme28.05.201314.941507.11−111
01.09.201415.825107.36−11.1
5328.840040.545776YalovaArmutlu kapl.well31.05.201374.626406.23174 x
5428.843140.546587YalovaArmutlu IPA2well 500 m x
5528.843240.546582YalovaArmutlu springspring01.06.201358.826006.4064
5628.840240.545578YalovaArmutlu near bridgewell, artesian01.06.201375.630106.2969 x
5729.277840.5939178YalovaSoğucak Aci Suspring31.05.201321.411196.75365
5829.171240.6038132YalovaTermal “Göz Suyu”Çesme31.05.201359.718707.57174
5929.170540.6039136YalovaTermal Kapl.spring31.05.201363.418207.3549
Table 2. Water geochemistry. The chemical and isotopic composition of the water samples are listed, pCO2 in bars, ion concentrations in meq/L, isotopic ratios in δ ‰ vs SMOW. The sea water composition is taken by https://www.britannica.com/science/seawater (accessed on 1 February 2025). See text for water-type classification. Empty cells = below detection limits; n.a. = not analyzed.
Table 2. Water geochemistry. The chemical and isotopic composition of the water samples are listed, pCO2 in bars, ion concentrations in meq/L, isotopic ratios in δ ‰ vs SMOW. The sea water composition is taken by https://www.britannica.com/science/seawater (accessed on 1 February 2025). See text for water-type classification. Empty cells = below detection limits; n.a. = not analyzed.
IDSiteDatepCO2LiNaKMgCaFClNO3SO4HCO3δ18Oδ2HWater Type
1Edremit03.09.20140.030.049.640.280.010.750.372.070.017.131.20−6.79−47.00Na-SO4
2Ekşidere03.09.20140.13 0.450.050.902.390.020.21 0.353.20−9.12−59.00Ca-HCO3
3Ekşi.Genc03.09.2014 0.500.040.150.700.000.42 0.920.05−8.97−51.00acid-SO4
4Ilica (Balya)29.05.20130.050.1010.400.120.010.840.402.510.167.231.57−10.25−70.16Na-SO4
5Ilicaboğazi30.05.20130.440.1025.970.431.834.160.0521.210.012.039.97−9.23−58.71Na-Cl
04.09.20140.400.0724.150.491.694.170.0519.780.061.899.10−9.32−58.00Na-Cl
6Kızık30.05.20130.460.1511.700.730.956.790.038.390.011.8410.94−8.17−55.48Na(Ca)-HCO3(Cl)
7Çepni04.06.20130.680.041.100.102.9721.600.010.440.080.0525.55−11.10−75.72Ca-HCO3
8Derdin04.06.20130.810.2081.821.115.817.170.779.490.0126.3262.94−8.39−70.63Na-Cl
9Efteni04.06.20130.790.1316.020.3112.417.170.044.47 0.0131.38−11.08−75.16Na(Mg)-HCO3
10Ilica (Taşk.)05.06.20130.020.047.660.110.075.820.050.32 13.390.38−13.11−88.17Na(Ca)-SO4
11Mudurnu05.06.20130.530.040.960.154.159.020.060.17 0.5714.10−11.87−78.98Ca(Mg)-HCO3
12Mudur NW05.06.20130.510.040.940.154.168.690.060.13 0.5913.82−11.61−77.67Ca(Mg)-HCO3
13Mudurnu NE05.06.20130.570.040.990.154.349.150.060.11 0.6214.55−11.71−78.36Ca(Mg)-HCO3
14Çekirge30.05.20130.270.011.250.111.734.130.040.13 1.226.10−10.94−70.34Ca-HCO3
04.09.20140.230.011.490.221.813.280.820.150.011.194.90−10.72−71.00Ca-HCO3
15Kükürtlü Uni03.06.20130.490.129.660.480.784.960.240.320.055.6310.55n.a.n.a.Na(Ca)-HCO3(SO4)
08.09.20140.390.098.880.500.704.510.240.340.015.558.70−9.79−71.00Na(Ca)-HCO3(SO4)
16Kükürtlü BK203.06.20130.160.139.960.520.652.410.240.290.012.0511.78−10.81−71.08Na-HCO3
08.09.20140.090.1010.650.570.681.070.230.31 0.5512.00−10.51−77.00Na-HCO3
17Kükürtlü BJ-303.06.20130.060.056.160.150.691.070.020.09 1.186.45−10.38−67.71Na-HCO3
18Çaybaşi UMS05.09.20140.580.478.160.786.219.620.122.510.120.6421.80−8.78−65.00Ca(Mg)-HCO3
19Çaybaşi ÖMS08.09.20140.550.142.920.269.474.310.040.990.010.6815.40−9.26−61.00Mg(Ca)-HCO3
20Oylat10.06.20130.140.040.970.120.686.510.030.160.024.973.49−10.78−69.65Ca-SO4(HCO3)
21Özlüce10.06.20130.670.1111.400.3811.379.750.020.66 1.2830.23−11.16−75.50Na(Mg)-HCO3
22Kınık10.06.20130.570.1514.320.565.969.900.020.700.060.9927.82−11.10−76.11Na(Ca)-HCO3
23Kınık N10.06.20130.820.4665.542.695.7510.040.011.86 2.0573.43−12.06−89.28Na-HCO3
24Çitli (Inegöl)10.06.20130.880.4790.321.126.4112.860.021.73 2.0398.94−11.76−88.60Na(HCO3)-Cl
25Yk. Gölüce02.06.20130.130.0836.140.441.761.540.3732.830.052.224.95−10.80−73.73Na-Cl
26Keramet02.06.20130.380.041.150.052.897.670.020.370.010.5811.37−10.19−65.02Ca(Mg)-HCO3
27Çakırlı02.06.20130.110.042.610.041.423.420.010.62 0.037.02−12.37−81.31Ca(Mg)-HCO3
28Orhangazi02.06.20130.23 0.430.030.467.36 0.350.340.437.48−9.54−59.18Ca-HCO3
29Gemlik03.06.20130.150.000.510.031.283.260.010.470.030.234.50−10.22−63.22Ca-HCO3
30Dümbüldek30.05.20130.820.1618.611.722.267.930.081.63 0.1129.03−10.50−68.49Na(Ca)-HCO3
31Dümb. spr.30.05.20130.770.1616.521.533.9316.730.061.72 1.6835.50−10.47−68.39Na(Ca)-HCO3
04.09.20140.680.1315.721.473.6014.850.041.740.011.7731.00n.a.n.a.Na(Ca)-HCO3
32Yalıntaş04.09.20140.630.1312.141.212.678.370.091.680.011.1621.70−10.73−76.00Na(Ca)-HCO3
33Kestanbol02.09.20140.482.45271.318.135.2443.230.48336.70.353.705.00−6.69−40.00Na-Cl
34Tuzla02.09.20140.092.74547.033.104.1097.31 660.00.252.270.15n.a.n.a.Na-Cl
35Kirkgecit29.05.20130.020.026.360.050.010.260.431.230.053.441.83−9.72−61.35Na-SO4
36Bardakcilar29.05.20130.040.0512.700.170.024.210.290.86 15.320.94−9.49−61.63Na(Ca)-SO4
37Hidirlar29.05.20130.120.057.880.170.020.870.360.46 6.831.66−8.32−51.30Na-SO4
03.09.20140.060.018.060.200.010.850.380.470.017.121.20n.a.n.a.Na-SO4
38Inönü Ilica09.06.20130.130.040.370.021.792.930.010.110.100.104.92−11.13−75.57Ca-HCO3
39Eskişehir09.06.20130.170.040.620.042.672.470.010.180.050.285.36−10.25−72.82Mg(Ca)-HCO3
40Uyush. E-808.06.20130.630.066.970.194.7911.530.021.650.120.5121.35−10.91−79.95Ca(Mg)-HCO3
41Uyushamam08.06.20130.490.041.790.217.776.750.020.610.010.9514.28−10.11−72.02Mg(Ca)-HCO3
42H.karahisar08.06.20130.24 1.820.091.745.250.011.020.070.367.56−10.68−73.82Ca-HCO3
43Tuzla Içmeler31.08.20140.22 104.02.0525.3617.67 130.80.1312.845.10n.a.n.a.Na-Cl
44Yeniköy04.06.20130.020.043.330.010.040.300.031.09 0.691.92−9.92−63.21Na-HCO3
45Yenik. Jazlik04.06.20130.020.043.120.010.030.290.020.770.010.672.14−9.77−62.45Na-HCO3
46Kuzuluk W31.08.20140.820.7274.212.479.8210.69 32.830.020.5865.003.56−44.00Na-Cl
47Kuzuluk K-331.08.20140.630.3730.281.071.194.730.239.710.011.1626.80−9.07−86.00Na-HCO3
48Ahibaba05.06.20130.530.0713.440.461.252.500.040.56 1.2415.33−10.87−70.64Na-HCO3
49Taraklı05.06.20130.410.041.150.111.656.870.040.21 0.339.49−11.66−77.14Ca-HCO3
50Hoşköy ÖMS01.09.20140.580.1242.080.392.222.790.131.600.010.2145.30n.a.n.a.Na-HCO3
51Yayaköy28.05.20130.230.11136.60.4710.066.360.07132.60.535.927.40−8.80−56.91Na-Cl
52Gölcük28.05.20130.210.0425.540.136.799.740.0429.63 6.248.06−8.08−51.51Na(Ca)-Cl
01.09.20140.16 14.820.165.055.210.0610.600.027.976.70−8.33−50.00Na(Ca)-Cl
53Armutlu31.05.20130.640.2115.320.751.8114.880.117.50 17.139.19−10.81−69.62Na(Ca)-SO4
55Armutlu spr.01.06.20130.530.1913.350.641.8413.200.096.440.0114.359.16−10.46−67.18Na(Ca)-SO4
58Termal Göz31.05.20130.240.010.450.062.7611.260.010.24 0.3014.67−9.84−60.63Ca-HCO3
59Termal31.05.20130.110.0511.930.110.048.450.102.43 16.641.26−11.23−70.72Na(Ca)-SO4
Iznik Lake02.06.2013 4.700.305.500.60 1.90 0.608.40
Sea water 464.310.11105.120.44 539.70.8355.830.45
Table 3. Chemical composition of the dissolved gases. Data in ccSTP/LH2O. Total volume in milliliters of gas per liter of water. Empty cells indicate values below detection limits. Carbon isotopic composition of TDIC in δ ‰ vs PDB. Empty cells = below detection limits; n.a. = not analyzed.
Table 3. Chemical composition of the dissolved gases. Data in ccSTP/LH2O. Total volume in milliliters of gas per liter of water. Empty cells indicate values below detection limits. Carbon isotopic composition of TDIC in δ ‰ vs PDB. Empty cells = below detection limits; n.a. = not analyzed.
IDSiteDateHeNeH2O2N2COCH4CO2Vol.δ13CTDCN2/O2He/NeR/Ra
1Edremit03.09.20147.8 × 10−43.0 × 10−42.5 × 10−46.018.42.7 × 10−53.0 × 10−20.424.8n.a.32.592.60
2Ekşidere03.09.20141.3 × 10−43.0 × 10−4 6.018.27.0 × 10−6 5.129.2−1.4530.430.43
3Ekşi. Gencli03.09.20148.9 × 10−52.9 × 10−44.8 × 10−44.517.3 4.0 × 10−170.392.5n.a.40.300.30
5Ilicaboğazi30.05.20132.9 × 10−43.3 × 10−48.4 × 10−47.019.67.3 × 10−52.5 × 10−373.3100.01.5230.870.95
04.09.20141.3 × 10−32.4 × 10−41.1 × 10-35.921.56.4 × 10−52.1 × 10−378.2105.5−0.8545.301.00
6Kizik30.05.20131.3 × 10−33.3 × 10−4 1.313.76.9 × 10−61.1 × 10−385.4100.4−3.43103.850.52
10Ilica05.06.20134.3 × 10−43.6 × 10−45.3 × 10−51.46.01.4 × 10−55.9 × 10−20.07.5n.a.41.170.63
11Mudurnu05.06.20131.0 × 10−42.1 × 10−4 0.34.1 70.374.7n.a.140.511.41
13Mudurnu NE05.06.20133.5 × 10−42.8 × 10−4 0.42.97.3 × 10−6 52.055.4n.a.71.251.85
14Çekirge30.05.20131.6 × 10−43.8 × 10−4 2.211.01.3 × 10−52.5 × 10−312.325.60.6450.411.19
04.09.20144.6 × 10−42.4 × 10−4 5.316.1 3.1 × 10−317.639.0−3.1931.900.53
15Kükürtlü Uni03.06.20132.6 × 10−42.8 × 10−4 1.545.4 6.6 × 10−553.1100.00.04310.940.67
08.09.20144.5 × 10−43.5 × 10−4 8.030.3 5.5 × 10−278.2116.60.4841.260.57
16Kükürtlü BK203.06.20133.0 × 10−31.8 × 10−4 0.132.7 1.6 × 10+065.5100.0n.a.64916.61.05
08.09.20145.2 × 10−32.3 × 10−4 5.220.62.2 × 10−56.7 × 10−44.230.02.91422.30.43
17Kükürtlü BJ-303.06.20132.3 × 10−43.2 × 10−41.8 × 10−40.54.0 2.5 × 10−40.85.3n.a.70.720.67
18Çaybaşi UMS05.09.20141.3 × 10−41.1 × 10−4 5.812.82.5 × 10−5 525.45442.8421.190.84
19Çaybaşi ÖMS08.09.20142.4 × 10−42.4 × 10−4 9.322.81.6 × 10−5 539.95721.9121.040.92
20Oylat10.06.20136.7 × 10−42.3 × 10−41.7 × 10−50.62.54.1 × 10−6 1.24.3n.a.42.930.70
21Özlüce10.06.20131.0 × 10−42.3 × 10−41.1 × 10−20.40.74.5 × 10−63.4 × 10−5246.6248n.a.20.430.95
22Kınık10.06.20131.4 × 10−42.8 × 10−41.6 × 10−30.52.6 3.7 × 10−4116.0119.0n.a.60.490.78
25Yk. Gölüce02.06.20138.5 × 10−52.0 × 10−4 n.a. 0.420.86
28Orhangazi02.06.20131.1 × 10−43.0 × 10−48.5 × 10−51.44.1 11.316.7n.a.30.380.97
29Gemlik03.06.20139.0 × 10−52.6 × 10−4 0.73.26.8 × 10−69.8 × 10−52.16.0n.a.40.350.94
30Dümbüldek30.05.20131.0 × 10−42.3 × 10−4 1.33.05.2 × 10−54.2 × 10−3221.9226−6.4720.431.12
31Dümbüldek sp.30.05.20131.1 × 10−43.0 × 10−4 5.611.01.0 × 10−44.2 × 10−4274227590.6720.351.15
04.09.20141.3 × 10−41.1 × 10−4 5.812.82.5 × 10−5 525.4544n.a.21.190.84
32Yalıntaş04.09.20145.3 × 10−31.1 × 10−4 17.542.9 9.2 × 10−3936.79973.52249.70.90
33Kestanbol02.09.20145.2 × 10−32.8 × 10−41.3 × 10−38.732.25.3 × 10−42.1 × 10−1125.7167−1.71418.20.87
37Yenice Hidirlar03.09.20147.8 × 10−43.0 × 10−42.5 × 10−46.018.42.7 × 10−53.0 × 10−20.424.8−13.8632.590.47
38Inönü09.06.20131.2 × 10−43.2 × 10−41.3 × 10−40.92.54.2 × 10−6 1.44.9n.a.30.360.95
39Eskişehir09.06.20131.3 × 10−42.9 × 10−49.2 × 10−30.83.1 1.75.7n.a.40.440.91
42Hamam. Çardak08.06.20134.3 × 10−41.2 × 10−33.2 × 10−40.63.22.7 × 10−6 6.510.2n.a.60.360.87
43Tuzla Içmeler31.08.20141.7 × 10−31.5 × 10−47.7 × 10−47.319.04.0 × 10−5 14.640.9n.a.311.40.59
44Yeniköy04.06.20136.3 × 10−33.8 × 10−41.2 × 10−30.24.53.3 × 10−6 0.04.7n.a.1916.90.74
45Yeniköy Jazlik04.06.20131.4 × 10−33.5 × 10−4 0.43.71.7 × 10−63.2 × 10−50.04.2n.a.84.120.53
46Kuzuluk W31.08.20142.1 × 10−38.6 × 10−5 n.a. 24.30.64
47Kuzuluk K-331.08.20141.6 × 10−43.0 × 10−44.2 × 10−36.920.0 3.9 × 10−2101.0127.9n.a.30.520.63
49Tarakli05.06.20131.4 × 10−42.6 × 10−4 0.93.43.1 × 10−61.5 × 10−521.125.4n.a.40.530.68
50Hoşköy ÖMS01.09.20143.2 × 10−41.2 × 10−4 0.112.5 320.8333n.a.2282.754.43
51Yayaköy28.05.20137.7 × 10−51.8 × 10−4 8.128.24.2 × 10−55.5 × 10−063.9105.6n.a.30.432.08
52Gölcük28.05.20138.3 × 10−52.5 × 10−4 0.038.21.2 × 10−52.7 × 10−012.323.2−17.472380.340.94
01.09.20146.1 × 10−52.0 × 10−4 2.914.71.6 × 10−4 18.736.3n.a.50.310.76
53Armutlu kapl.31.05.20131.2 × 10−44.1 × 10−4 0.61.91.0 × 10−58.7 × 10−229.932.5−3.7330.290.87
55Armutlu spring01.06.20136.1 × 10−43.2 × 10−42.1 × 10−40.72.02.1 × 10−6 39.742.4n.a.31.910.34
58Termal Göz31.05.20131.4 × 10−42.2 × 10−4 2.16.71.3 × 10−57.4 × 10−518.427.2n.a.30.650.70
59Termal31.05.20131.3 × 10−33.4 × 10−4 1.46.13.5 × 10−6 0.37.8n.a.44.000.34
ASW 4.8 × 10−5 4.89.6 1.0 × 10−62.416.8 2
Table 4. Chemical composition of the bubbling gases. Data in vol%. 40Ar in ppm by vol. Carbon isotopic ratios in δ ‰ vs. PDB. Helium isotopic ratios expressed as R/Ra (see text). δ13C values refer to CO2.Empty cells indicate values below detection limits; n.a. = not analyzed.
Table 4. Chemical composition of the bubbling gases. Data in vol%. 40Ar in ppm by vol. Carbon isotopic ratios in δ ‰ vs. PDB. Helium isotopic ratios expressed as R/Ra (see text). δ13C values refer to CO2.Empty cells indicate values below detection limits; n.a. = not analyzed.
SiteDateHeNeH2O2N2COCH4CO2δ13CHe/NeR/Ra40Ar40/36ArCO2/3He
Ilica Çamur29.05.20136.7 × 10−41.9 × 10−34.4 × 10−8 95.3 2.4 × 10−12.7−17.20.360.971.8298.62.9 × 109
Çepni04.06.20137.0 × 10−41.9 × 10−3 1.76.62.0 × 10−53.2 × 10−491.5−1.80.370.950.2300.59.9 × 1010
Derdin04.06.20134.1 × 10−44.1 × 10−4 0.31.64.0 × 10−53.3 × 10−398.1−4.21.000.72n.a.n.a.2.4 × 1011
Efteni04.06.20136.6 × 10−41.8 × 10−31.3 × 10−70.01.41.8 × 10−58.0 × 10−197.8−3.30.370.98n.a.n.a.1.1 × 1011
Mudurnu NW05.06.20131.1 × 10−31.5 × 10−39.0 × 10−813.762.1 1.4 × 10−223.4−5.20.781.600.9298.89.2 × 109
Lues refer to COKükürtlü BK203.06.2013 6.1 × 10−3 33.54.3 × 10−41.2 × 10065.2−5.2n.a.n.a.n.a.n.a.
Kınık N10.06.20135.9 × 10−31.9 × 10−4 0.12.42.0 × 10−51.1 × 10−397.4−3.730.80.520.1296.22.3 × 1010
Çitli10.06.20131.1 × 10−21.0 × 10−3 0.44.8 3.9 × 10−394.5−6.210.10.520.3301.91.2 × 1010
Keramet02.06.20132.7 × 10−32.1 × 10−3 2.082.33.0 × 10−53.1 × 10−315.7−9.41.280.47n.a.n.a.8.9 × 109
Çakırlı02.06.20136.5 × 10−42.0 × 10−3 8.9 9.1 × 1010.1−14.30.320.97n.a.n.a.1.5 × 108
Dümbüldek sp.30.05.20131.7 × 10−44.2 × 10−4 1.64.53.0 × 10−59.6 × 10−393.9−5.00.400.98n.a.n.a.4.1 × 1011
Dümbüldek sp.04.09.20141.0 × 10−36.4 × 10−5 1.75.31.1 × 10−42.6 × 10−293.0n.a.15.51.18n.a.n.a.5.7 × 1010
Tuzla02.09.20141.4 × 10−32.9 × 10−5 0.51.59.0 × 10−42.1 × 10−197.8n.a.47.71.54n.a.n.a.3.3 × 1010
Kirkgecit29.05.20133.7 × 10−21.5 × 10−32.6 × 10−70.496.99.0 × 10−43.7 × 10−11.1n.a.24.80.181.2294.61.2 × 108
Bardakcilar29.05.20136.0 × 10−21.5 × 10−31.1 × 10−61.693.82.2 × 10−32.9 × 10−13.0n.a.40.10.201.3294.91.8 × 108
Yenice Hidirlar29.05.20136.4 × 10−31.4 × 10−34.0 × 10−80.493.66.0 × 10−43.3 × 10−14.1n.a.4.440.181.6294.62.6 × 109
Yenice Hidirlar03.09.20144.3 × 10−23.9 × 10−31.8 × 10−30.397.81.2 × 10−43.3 × 10−11.5n.a.11.00.17n.a.n.a.1.5 × 108
Uyusham. E-808.06.20131.3 × 10−31.7 × 10−3 0.74.73.0 × 10−51.1 × 10−294.2n.a.0.720.720.4302.97.5 × 1010
Uyushamam08.06.20133.3 × 10−21.4 × 10−3 0.460.32.0 × 10−53.6 × 10−238.3−2.523.60.660.9299.21.2 × 109
Kuzuluk W31.08.20141.8 × 10−22.0 × 10−5 0.34.49.0 × 10−51.993.4n.a.8970.65n.a.n.a.5.8 × 109
Kuzuluk K-331.08.20146.7 × 10−31.9 × 10−5 0.12.43.0 × 10−58.2 × 10−196.7n.a.3460.63n.a.n.a.1.7 × 1010
Armutlu kapl.31.05.20136.4 × 10−42.1 × 10−3 0.037.7 1.361.0−1.60.310.93n.a.n.a.7.4 × 1010
Armutlu IPA201.06.20131.0 × 10−11.1 × 10−32.5 × 10−8 70.01.0 × 10−55.3 23.7−2.790.30.200.9294.38.5 × 108
Armutlu well01.06.20131.7 × 10−21.6 × 10−3 6.142.67.0 × 10−51.349.3−1.110.50.260.7299.28.3 × 109
Termal Göz05.06.20138.0 × 10−34.4 × 10−4 0.422.5 9.5 × 10−376.6−6.118.30.110.5303.26.1 × 1010
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Italiano, F.; Woith, H.; Pizzino, L.; Sciarra, A.; Seyis, C. Geochemical and Isotopic Features of Geothermal Fluids Around the Sea of Marmara, NW Turkey. Geosciences 2025, 15, 83. https://doi.org/10.3390/geosciences15030083

AMA Style

Italiano F, Woith H, Pizzino L, Sciarra A, Seyis C. Geochemical and Isotopic Features of Geothermal Fluids Around the Sea of Marmara, NW Turkey. Geosciences. 2025; 15(3):83. https://doi.org/10.3390/geosciences15030083

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Italiano, Francesco, Heiko Woith, Luca Pizzino, Alessandra Sciarra, and Cemil Seyis. 2025. "Geochemical and Isotopic Features of Geothermal Fluids Around the Sea of Marmara, NW Turkey" Geosciences 15, no. 3: 83. https://doi.org/10.3390/geosciences15030083

APA Style

Italiano, F., Woith, H., Pizzino, L., Sciarra, A., & Seyis, C. (2025). Geochemical and Isotopic Features of Geothermal Fluids Around the Sea of Marmara, NW Turkey. Geosciences, 15(3), 83. https://doi.org/10.3390/geosciences15030083

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